1. Field of the Invention
The present invention relates generally to semiconductor integrated circuit manufacturing and, more particularly, to a method for forming a conformal insulation film constituted by, e.g., amorphous silicon or silicon nitride on a semiconductor substrate by plasma-enhanced atomic layer deposition (PEALD).
2. Description of the Related Art
For forming a silicon nitride by atomic layer deposition (ALD), a halide precursor is often used. This is because a halide precursor, especially a precursor containing chlorine, is characterized by its easy substitution treatment by heat reaction with NH3. Since the reactivity of NH3 or H2 with a halide precursor is very high, unwanted deposition occurs inside an exhaust pipe or particles are generated as a result of mixing with other gases when a process takes place. Thus, to deal with the above problems, extra attention needs to be paid to the process conditions, and special modifications to the process sequence are required, and additional consideration of prevention of unwanted depositions to exhaust pipes is also required. Accordingly, the above methods face not only the cost increase problem but also the productivity decrease problem due to the process sequence being more complex and the process duration being prolonged.
Further, when a halide precursor is used, reactivity of substitution reaction with reactant gas depends on the reaction temperature, and when the reaction temperature is 300° C. or lower, reactivity with the reactant gas suffers, and step coverage which is also temperature-dependent tends to be lower than 90%.
Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for some, not all, embodiments of the present invention, and it should not be taken as an admission that any or all of the discussion were known at the time the invention was made.